Here's a dimension idea for a contest that I participated in a while ago (it won).

Dimension Idea: Abbadon

Abbadon is a bleak wasteland with rivers of bile. The grass is a sickly yellow color and the occasional mountains can be seen.

Structures:

Temple of the Apocalypse- A temple with five levels and different spawners on each level. The top has the altar for the bosses, the fourth floor has Olethrodaemon spawners, the third floor has Purrodaemon spawners, the third floor has Meladaemon spawners,and the first floor has Leukodaemon spawners.

Charon's Ferry- A large boat with numerous Thanadaemon spawners and a Charon Altar.

A near flat landscape on the surface. There are small hills but they are few and far between. Pieces of an old civilization can be found in the form of ruins as well as shrines to the God kept in immaculate condition by whichever God controls the realm. Underground is a different story however, it is populated with many creatures all designed for underground living. There are huge cities that hang from the roofs of incredibly tall and wide caves all connected by smaller caves on various levels on the city.

Structures:

On the surface:

Small derelict house.

These are very frequent on the surface and are usually on the hill that the surface has. Very dilapidated

Large derelict house.

The same thing as the small house except larger, rarer and better loot.

Dereloid nest.

A nest of the hunger job Dereloid. Has 4 spawners and the nest itself is a plus shape. It is only enterable via the sides and the middle contains the loot.

God temple.

a mint condition aincient temple created by the previous civilisation. The boss rocust can be fought here.

Underground.

Top/mid/low tier house.

The basic hanging houses in the various cities. The lower down, the better the loot.

Central beacon.

A power supplying spire at the center of each city. Destroying the core inside breaks all the lights and any machinery stops working in that city.

Mid/low tier factory.

These are used to craft certain items. One of these will spawn the boss of the realm.

Mid/low tier merchant.

These contain merchants for various things like guns, coins, food ect.

Low tier government building.

These exist only in the bottom later and contain great valuables.

Mobs:

On the surface

Dereloid.

These are small creatures with a huge opening mouth. They have ten small legs making them extremely fast and agile. Hostile

Sfant.

A creature the same size as a player but with four arms on each face of a rectangular body.

Underground.

Etarian.

A clawed legged creature with a hat made of the same material as turtle backs. They are brown however. These creatures live in the city.

Etarian merchant.

An etarian that sells different items. Their bib/robe shows what they sell.

Etarian government official.

Strong. Has body guards and only spawns on the lowest layer. Drops good loot when killed.

Etarian body guard.

Protects etarian government official.

Etarian electrician.

They spawn in the lower supply spire. Will attack if you get too close to the core.

Caveworm.

Live in the caves connecting the cities. If attacked, they become hostile. If not killed quick enough they can duplicate. Have good drops.

Side effects.

if on the surface for too long, particles of dirt appear on the screen with the message:

Dust carried by the wind catches your eye.

If you go down too far in the caves, you will begin to take damage with the message:

Your lungs are sparce due to the lack of oxygen.

Bossess:

Rocust.

The overground boss. He summoned when a dust share is placed on a dust altar.

Cave creature.

The underground boss. Summoned when a piece of the core is placed on a cave altar.

My idea is not about new things, it's about config. I want to set which nights will be these nights with ghosts. For example when I want to have ghost night (or however is this called) every 2 days, I will type 2 in config. Also I would like to have an option to set the first night when it will appear so it will not clash with Random Things mod's Bloodmoon. For example I will set first number to 4 and second number (when first ghost night appears) to 2 and the nights will look like this: normal, ghost, normal, blood. Why do I want it? It's for my modpack.

Edit: Oh and also do this with other events, not only ghost. When I first posted this I didn't know about other events.